Ratcheting Torque Wrench

ABSTRACT

A tool is provided for driving fasteners that includes a torque limiting mechanism therein. The torque limiting mechanism includes a first frictional engagement member disposed on the drive shaft for the tool that is engaged by one or more second frictional engagement members disposed on one or more sides of the first frictional member. The second frictional engagement members are biased into engagement with the first member by biasing members disposed within the handle that can be adjusted in order to provide more or less of a biasing force to control the frictional engagement of the second member with the first member and thereby control the torque limiting function of the torque limiting mechanism. In addition, a drive shaft is also engaged with a ratcheting mechanism that enables the tool to drive a fastener into a suitable substrate in only a single direction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority as a continuation-in-part applicationfrom U.S. patent application Ser. No. 11/645,942, filed Dec. 27, 2006,which is a continuation of U.S. patent application Ser. No. 11/232,634,filed Sep. 22, 2005, now U.S. Pat. No. 7,014,023, which is acontinuation of U.S. patent application Ser. No. 10/969,402, filed onOct. 20, 2004, now U.S. Pat. No. 6,948,605, which is a continuation ofU.S. patent application Ser. No. 10/342,707, filed on Jan. 15, 2003, nowU.S. Pat. No. 6,817,458, which claims priority from U.S. ProvisionalPatent Application Ser. No. 60/348,516, filed on Jan. 16, 2002, as wellas from U.S. Provisional Patent Application Ser. No. 60/802,747, filedon May 23, 2006.

FIELD OF THE INVENTION

The present invention relates to torque wrenches, and, morespecifically, to a torque wrench including both a torque limitingmechanism and a ratcheting mechanism disposed within the handle of thewrench.

BACKGROUND OF THE INVENTION

In order to drive a screw or other fastener into a substrate, wrenches,such as torque wrenches are often utilized. Torque wrenches are utilizedprimarily because of their capability to control the amount of torquethat can be applied to the fastener while the fastener is being driveninto the substrate. Thus, the fastener can be driven into the substratewith the desired level of torque, thereby preventing damage from beingdone to the substrate as a result of overdriving the fastener into thesubstrate.

To accomplish this, a number of different torque limiting mechanismshave been developed for implementation within torque wrenches that allowthe fastener-engaging portion of the wrench to slip with regard to thedriving portion of the wrench when a preset maximum torque value hasbeen exceeded.

However, with the majority of torque limiting mechanisms available,these mechanisms utilize friction as the primary source to developtorque on the mechanism. Therefore, it is desirable to develop animproved torque limiting mechanism that greatly lessens the amount offriction required in order to generate the torque in the torque limitingmechanism, such that the wear on the tool and torque limiting mechanismis reduced, lengthening the life of the tool.

Also, prior torque limiting mechanisms are limited in the amounts oftorque value adjustments that can be made as a result of the particularconstruction of the mechanisms. Thus, it is also desirable to develop animproved torque limiting mechanism that enables finer adjustments of thetorque limiting values at which the mechanism can operate.

In addition, a number of wrenches in use employ a ratcheting mechanismto enable the wrench to be used to selectively drive or remove afastener from a substrate. These mechanisms enable the wrench to berotated in only one direction, such that the wrench can only be rotatedin the direction that either drives or removes the fastener from thesubstrate as desired.

However, while the ratchet tools currently used in the medical field andin other areas are capable of tightening screws and other fasteners, anyprior art ratchet tools suffer from a number of problems that preventthe tools from being utilized most efficiently. One problem is thatoften times it is difficult for an individual using the ratchet tool todetermine when the fastener is tightened to the proper amount based as aresult of the construction of the ratchet tool. More specifically, mostratchet tools have a “sloppy feel” as a result of their design, whichprevents an individual from feeling the resistance exerted on the toolby the fastener in order to accurately determine when the fastener isproperly tightened. Also, when external attachments or shaft couplersare connected to the tool, the loss of feel when utilizing the tool iscompounded.

Further, another problem associated with prior art ratchet tools arisesdue to the positioning of the central gear within the tool. Moreparticularly, when the tool has been used for a certain amount of time,the central gear in the ratcheting mechanism tends to move out ofconcentricity with the handle of the tool, such that the gear “runs out”with regard to the handle, thereby limiting the effectiveness of thetool.

Finally, another shortcoming of the prior art ratchet tools arisesbecause tools utilized in medical scenarios must be sterilized betweenuses. Based on the open construction of prior art tools, the use ofcleaning solutions to sterilize tools of this type often times cannotadequately clean the internal portions of the tool such that the toolretains dirt or other debris, including residual cleaning fluid, withinthe interior of the mechanism which can significantly affect the abilityoperation of the tool to be used.

Therefore, it is desirable to develop a torque wrench tool that includesboth an improved torque limiting mechanism optionally in conjunctionwith an improved ratcheting mechanism to allow for the finer adjustmentof the maximum torque values for the tool, as well as enabling the toolto provide adequate feel of the resistance of the fastener through thetool. The improved ratchet tool construction should also effectivelyprevent any run out of the central gear with respect to the tool, whilealso effectively sealing off the interior of the tool from the exteriorof the tool such that no fluid, gas or debris can get into the tool andaffect the operation and/or usefulness of the tool.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, a driving toolincludes a drive shaft disposed within a housing forming a handle forthe tool. The drive shaft that is formed with an inner portion having anengaging ring disposed around the inner portion. The engaging ringincluding a number of engaging surfaces, such as slots, spaced aroundthe periphery of the engaging ring. The inner portion of the drive shaftand the engaging ring are inserted within the handle housing such thatthe drive shaft is rotatable with respect to the handle. On oppositesides of the handle are disposed additional engaging surfaces or membersthat can contact the engaging surfaces on the engaging ring. Theadditional engaging surfaces can take various forms, such as plungersthat hold a number of elongate pins therein that are selectivelyengageable with the engaging surfaces on the engaging ring. Thisprovides the torque limiting mechanism with an opposed constructioninstead of an in-line construction to provide the handle incorporatingthe torque limiting mechanism with a low profile. However, theconstruction of the tool can also incorporate the torque limitingmechanism in an in-line construction, if desired. The engaging surfaceson the plungers are urged into engagement with the engaging surfaces onthe engaging ring secured to the drive shaft by biasing membersextending between the plungers and end caps affixed to opposed ends ofthe handle. The bias of the springs urges the plungers and engagingsurfaces thereon into engagement with the slots to enable the engagingring and the drive shaft to rotate in conjunction with the handle todrive the fastener into the substrate. However, should the torquetransmitted through the drive shaft to the handle and plungers exceedthe biasing force of the biasing members, the torque created by therotation of the drive shaft will cause the drive shaft to push theengaging surfaces on the plungers past or out of engagement with thesurfaces on the engaging ring, allowing the drive shaft to rotateindependently of the handle. This mechanism greatly reduces the frictionand resulting wear in the mechanism, lengthening the useful life of thetool.

According to still a further aspect of the present invention, theconfiguration of the engaging surfaces, e.g., depth of the slots on theengaging ring secured to the drive shaft, can be varied to increase ordecrease the torque values that are provided by the mechanism for thetool without varying the biasing members utilized in the construction ofthe mechanism.

According to still another aspect of the present invention, the tool isadditionally formed with a ratcheting mechanism that includes a centralgear rotatably mounted within a recess formed in the outer portion ofthe drive shaft in a manner that prevents the gear from shifting axiallyor laterally with respect to the drive shaft. The gear is operablyconnected to the drive shaft opposite the inner portion and is locatedat least partially within the housing for the tool. The drive shaftsupports the central gear, which defines a central opening, into which ashaft extender or other fastener-engaging device can be inserted, andhas a number of teeth spaced around the periphery thereof. The shaft andthe gear are maintained in position within the housing by a bearingpositioned around the shaft adjacent the gear and engaged with thehousing opposite the shaft. The bearing includes a smooth or otherwiseessentially frictionless interior surface that is contacted by the shaftin order to enable the shaft to rotate freely with respect to thebearing. On the outer surface of the bearing, each bearing can include asealing member that is engaged with the housing to both secure thebearing with regard to the housing, thereby preventing the bearing andthe shaft positioned within the bearing from shifting with regard to thehousing during the operation of the tool, and to seal the interior ofthe housing inwardly from the bearings. Thus, the gear which is attachedto the shaft is prevented from shifting laterally or axially within thehousing.

Because the gear is maintained in both a lateral and axial position withrespect to the housing, the gear is maintained in proper alignment witha pair of pawls also disposed within the outer portion of the driveshaft and selectively engageable with the teeth on the exterior of thegear. Upon selectively engaging one or the other of the pawls with thegear, the rotation of the gear and the drive shaft can be controlled ordirected in either a counterclockwise or clockwise direction as desiredwhen operating the tool.

According to another aspect of the present invention, the ratchetingmechanism also includes a cap engageable with the bearing over therecess in which the mechanism is located that includes a centralaperture aligned with the central opening in the gear. The cap includesa sealing member disposed along the periphery of the central aperturethat sealingly engages the gear around the central opening in order toprovide a fluid tight seal therebetween. The cap also engages a sealingsurface disposed on the exterior of the housing around the recess onwhich another sealing member can be positioned in order to provide afluid tight seal between the bearing and the cap. Therefore, whencleaning the tool after use or using the tool in environments wherefluids are present, the fluids are prevented from penetrating past thebearing into the interior of the housing. As a result, no liquid, gas,debris or residual cleaning material is able to affect the normaloperation of the mechanism.

According to still another aspect of the present invention, themechanism can include a number of bearings disposed within the recessand around the gear depending on the torque to be applied using thetool. In situations where the torque to be applied is minimal, only onebearing may be necessary to prevent any run out of the central gear withrespect to the outer portion of the drive shaft. However, in situationswhere the tool is used to apply more torque to a fastener in order totighten or remove the fastener, additional bearings may be positionedwithin the recess to maintain the position of the gear within themechanism even with the increased torque applied from the tool.

Numerous other aspects, features, and advantages of the presentinvention will be made apparent from the following detailed descriptiontogether with the drawings figures.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate the best mode currently contemplated ofpracticing the present invention.

In the drawings:

FIG. 1 is an isometric view of a first embodiment of a torque wrenchconstructed according to the present invention including a torquelimiting mechanism;

FIG. 2 is a side plan view of the wrench of FIG. 1;

FIG. 3 is a cross-sectional view along line 3-3 of FIG. 2;

FIG. 4 is a cross-sectional view along line 4-4 of FIG. 1;

FIG. 5 is an isometric view of a first embodiment of the drive shaftutilized in the torque limiting mechanism of the wrench of FIG. 1;

FIG. 6 is an isometric view of a first embodiment of a plunger utilizedin the mechanism of FIG. 1;

FIG. 7 is a side plan view of a second embodiment of the tool of FIG. 1incorporating a second embodiment of a torque limiting mechanism and aratcheting mechanism;

FIG. 8 is a cross-sectional view along line 8-8 of FIG. 7;

FIG. 9 is an exploded isometric view of the tool of FIG. 7; and

FIG. 10 is an exploded isometric view of a third embodiment of thetorque limiting mechanism used in the tool of FIG. 7.

DETAILED DESCRIPTION OF THE INVENTION

With reference now to the drawing figures in which like referencenumerals designate like parts throughout the disclosure, a firstembodiment of a torque wrench constructed according to the presentinvention is indicated generally at 100 in FIG. 1. The wrench 100includes a handle 102 from which extends a shaft 104 having a driveshaft release member 106 attached thereto opposite the handle 102.Release member 106 is utilized to secure a drive shaft 108 thereto inorder to drive a fastener (not shown) that is engaged by thefastener-engaging shaft 108 into a substrate.

Looking now at FIGS. 3-5, the drive shaft 104 includes an outer section110 integrally connected to an inner section 112 that is positionedwithin the handle 102. The outer section 110 is generally cylindrical inshape and includes a number of circular openings 114 spaced equidistantaround the outer section 110. The openings 114 are adapted to receiveball bearings (not shown) therein that are used to engage and retain thefastener-engaging shaft 108 that is inserted into a central channel 115defined within the outer section 110. The ball bearings can be movedinto and out of the openings 114 and the channel 115 by the movement ofthe release member 106 in opposition to a spring 116 secured between theouter section 110 of the shaft 104 and the release member 106. When therelease member 106 is moved along the shaft 104 against the bias of thespring 116, the ball bearings can move into the openings 114 and out ofthe channel 115, thereby exposing the interior of the channel 115 toenable the fastener-engaging shaft 108 to be inserted therein. Once anotch (not shown) on the fastener-engaging shaft 108 is aligned with theopenings 114, the release member 106 can be released such that thespring 116 moves the release member 106 over the openings 114 into thechannel 115 to urge the ball bearings through the openings 114 andpartially into the notch, thereby holding the fastener-engaging shaft108 in connection with the shaft 104.

The inner section 112 of the shaft 104 includes an engaging ring 120that is disposed within the handle 102 around the inner section 112 inalignment with a longitudinal channel 121 that extends completelythrough the handle 102. The inner section 112 and engaging ring 120 arerotatably mounted within the channel 121 in the handle 102 by a rollerbearing 122 secured within the handle 102 and against which the engagingring 120 are pressed. Opposite the roller bearing 122, the engaging ring120 is held within the handle 102 by a wear ring 123 abutting theengaging ring 120, and on which the ring 120 can rotate, as well as anO-ring 124 and cover cap 126 that each defines a central opening 127therein through which the shaft 104 can extend outwardly from the handle102. The O-ring 124 and cap 126 operate to effectively seal off theinterior of the channel 121 in the handle 102, to prevent and dirt orother debris or moisture from entering the handle 102 and interferingwith the operation of a torque limiting mechanism 132, of which theengaging ring 120 forms a part.

The engaging ring 120 disposed on the inner section 112 of the shaft 104has an outer diameter greater than the diameter of both the outersection 110 and the remainder of the inner section 112, and includes anumber of engaging surfaces 128, such as longitudinal grooves, spacedtherearound. The grooves 128 are spaced equidistant from one anotheraround the entire periphery of the engaging ring 120, and define flatsections 130 between each adjacent pair of grooves 128. While thegrooves 128 are illustrated in the drawing figures as being generallyshaped as elongate ovals, the grooves 128 can have any desired orsuitable shape as well, such as circular in shape, or can be made tohave different shapes for adjacent grooves 128 to provide additionalfunctionality to the mechanism 132.

Referring now to FIGS. 3 and 4, in order to provide the torque limitingfunction with regard to the rotation of the engaging ring 120 on theinner section 112 of the shaft 104 with regard to the handle 102, abiasing member of the torque limiting mechanism 132 is disposed withinthe longitudinal channel 121 inside the handle 102 and engaged with theengaging ring 120. The mechanism 132 is entirely disposed within thehandle 102 and in a first embodiment includes a pair of plungers 134disposed adjacent opposite sides of the engaging ring 120. In aparticularly preferred embodiment best shown in FIG. 6, each plunger 134includes a body 136 having a generally circular cross-section anddefining a flat rear surface 138 and a concave front surface 140, thoughother configurations for the plunger 134 can also be utilized. Theconcave front surface 140 includes one or more engaging surfaces 144,preferably formed from which elongate pins 144 rotatably positionedwithin elongate slots 142 formed in the concave surface 140 of theplunger 134. The shape for the slots 142 and pins 144 corresponds to theshape of the groves 128 formed in the engaging ring 120. While threeslots 142 and pins 144 are illustrated in the drawings, a larger orsmaller number of slots 142 and/or pins 144 can be used in each plunger134. Further, the pins 144 can be located in any number of the slots142, such as in one or more of the outer slots 142 offset from thecenterline of the shaft 104. The spacing of the slots 142 in the concavesurface 140 of the plunger 134 defines flat sections 146 therebetweenthat correspond to the distance between the grooves 128 on the engagingring 120. The pins 144 held within the slots 142 have an overalldiameter greater than the depth of the slots 142, such that a portion ofthe pins 144, and preferably about half of the volume of each pin 144,projects outwardly from the slots 142 and into the grooves 128 on theengaging ring 120 on the inner section 112 of the shaft 104. While thegrooves 128 and pins 144 are the preferred construction for thisembodiment of the torque limiting mechanism 132, other configurationsfor the surfaces 128 and 144 are also contemplated as being within thescope of the present invention.

The plungers 134 and pins 144 are biased into engagement with thegrooves 128 on the engaging ring 120 by a pair of compression members148 that engage the rear surfaces 138 of each plunger 134. Thecompression members 148 exert a biasing force on the plungers 134 tourge the plungers 134 and the pins 144 in each plunger 134 into contactwith the grooves 128 in the engaging ring 120. The compression members148 can be formed as desired with a suitable configuration andcomponents to urge the plungers 134 toward the engaging ring 120 withthe appropriate level of force, but are preferably formed fromcompression springs 150, which can be a coil spring, or a number ofspring washers, among other suitable compression members. The springs150 extend through guide tubes 151 located within the channel 121adjacent the expanded section 120, and seat at one end around aprojection 152 extending outwardly from the rear surface 138 of the body136 to maintain the springs 150 operably connected to the plungers 134.Opposite the plungers 134, each spring 150 is held at the desired levelof compression to exert the desired force on the plungers 134 by an endcap 154 sealingly engaged with the handle 102 within each end of thelongitudinal channel 121. Each end cap 154 is sealingly engaged to thehandle 102 within the channel 121 by an O-ring 155, and includes thereonan adjustment nut 156 that extends into the channel 121 and can be usedto expand or contract the size of the end cap 154 such that the caps 154can be moved within the channel 121 to vary the amount of compressionprovided by the springs 150 against the plungers 134. The position ofthe nuts 156 can be determined or measured as necessary in any suitablemanner during assembly of the wrench 100, or alternatively during use ofthe wrench 100, to ensure that the maximum torque value for themechanism 132 is set as desired. Thus, the amount of force provided bythe springs 150 urging the plungers 134 and pins 144 into engagementwith the grooves 128 on the engaging ring 120 can be varied to set amaximum torque limit for the activation of the mechanism 132 wheredesired.

In operation, when this maximum torque value has been reached and/orexceeded by the force applied in the turning of the handle 102 to drivea fastener into a substrate by an individual, the force exerted to turnthe handle 102 will overcome the bias of the springs 150 urging theplungers 134 into engagement with the engaging ring 120. As a result,the force rotating the handle 102 and the plungers 134 and the pins 144,will cause the pins 144 and plungers 134 to move out of the grooves 128within which they are seated and towards the end caps 154 against thebias of the springs 150. As the pins 144 are moved out of the associatedgrooves 128, the handle 102 can rotate independently with respect to oraround the engaging ring 120 and shaft 104 until the pins 144 becomeseated in an adjacent groove 128.

In addition, while the depth of each of the grooves 128 on the engagingring 120 is preferably uniform, in an alternative embodiment the depthof each groove 128 can be varied to increase or decrease the volume ofthe pins 144 that can be seated in the grooves 128, consequently varyingthe torque values provided by the mechanism 132 from the springs 150,without physically changing the springs 150.

Referring now to FIGS. 7-9, a second embodiment of the wrench 100 isillustrated. In this embodiment, the drive shaft 104 is offset from thecenter of the handle 102. Thus, the drive shaft 104 andfastener-engaging shaft 108 are positioned closer to one side of thehandle 102, which allows the tool 100 to be utilized in locations wherethe previous embodiment of the tool 100 would be unworkable due to thelength of the handle 102 extending from opposite sides of the driveshaft 104.

Further, as best shown in FIG. 8, due to the extended length of one sideof the handle 102, the adjustment nut 156 is separated from the end cap154 and disposed entirely within the channel 121 to vary the compressionof the springs 150, thereby controlling the maximum torque level atwhich the mechanism 132 can be operated. In a preferred embodiment, theadjustment nut 156 is threadedly engaged with the interior of thechannel 121 such that the nut 156 can be advanced or retracted withinthe channel 121 to the desired location to vary the level of forceapplied by the compression members 148 on the plunger 134. Oncepositioned, the nut 156 can be secured at that position utilizing asuitable adhesive, or can be left unadhered, such that the nut 156 canbe readjusted as necessary. Additionally, to assist in keeping thecompression members 148 engaged with the nuts 156, each nut 156 can beformed with a forwardly facing stub (not shown) around which thecompression member 148 can be seated opposite the projection 152 on theplunger 134. The length of the stub is sufficient to hold thecompression member 148 on the nut 156 without affecting the biasingproperties of the compression member 148.

Looking again at FIGS. 7-9, in addition to the offset of the shaft 104in the handle 102, the handle 102 includes a separate housing extension200 located between opposed ends of the handle 102 and into which theshaft 104 extends from the handle 102. The housing 200 is disposed inalignment with the drive shaft 104 and encloses the portion of the driveshaft 104 extending outwardly from the channel 121. The housing 200includes an end cap 202 that defines an opening 203 therein throughwhich the fastener-engaging shaft 108 can be inserted for engagementwith the drive shaft 104. In this embodiment, the outer section 110 ofthe drive shaft 104 is formed to have a diameter slightly less than thatof the housing 200, such that the outer section 110 can be movablysecured within the housing 200 adjacent the end cap 202 by a bearing201. The bearing 201 is, in turn, secured to the housing 200 oppositethe handle 102 and defines a space therein for the shaft 104, such thatthe shaft 104 can rotate with respect to the bearing 201. Additionally,in order to form a liquid-tight seal around the interior components ofthe tool 100, a pair of sealing members 205 are disposed around theouter section 110 and the inner section 112 to effectively seal off theinterior of the tool 100. Also, to make the attachment of the shaft 104of the handle 102 more simple to construct, the handle 102 is formedwith an aperture 400 opposite the housing 200, thus forming a channelcompletely through the handle in which the drive shaft 104 is disposed.The inner section 112 of the drive shaft 104 is secured within theaperture 400 by a locking nut 402 positioned between the aperture 400and the inner section 112 of the drive shaft 104, which allows the shaft104 to rotate within the handle 102. The nut 402 and the shaft 104 areenclosed within the handle 102 by a back cap 404 that generally conformsto the shape and contours of the handle 102. With this cannulatedconstruction for the handle 102, the interior of the tool 100 can beaccessed as desired during operation and/or for cleaning purposes.

As best shown in FIGS. 8 and 9, the housing 200 also holds a ratchetingmechanism 218 and a collar 220 fixed at one end to the drive shaft 104and each positioned within the cap 202. The collar 220 is affixed to theouter section 110 of the drive shaft 104 opposite the inner section 112,and preferably is integrally formed with the outer section 110 of thedrive shaft 104.

The collar 220 includes a generally circular central opening 226 thatextends through the housing 220 in alignment with the central channel115 of the outer section 110 of the drive shaft 104. A pair of slots 228is disposed on opposite sides of the opening 226 and extend generallyradially and tangentially outwardly from the openings 226. However, theslots 228 can also be offset from one another such that the slots 228are not aligned or positioned as mirror images of each other. Each slot228 defines a nesting portion (not shown) opposite the central opening226 that is preferably generally circular or arcuate in shape, andcircumscribes an arc of greater than 180°. More preferably, the nestingportion encompasses an arc of greater than 200° but not more than 250°to allow for sufficient movement within the portions. However, the slots228 can be formed with any suitable configuration capable of functioningin the manner to be described.

The shape of each nesting portion is designed to pivotally receive andsecurely retain a pawl 232 therein. The pawls 232 are generally elongatemembers formed of a rigid material, such as a metal or hard plastic,that include a stem 234 having a generally circular cross-section and adiameter slightly less than the inner diameter of the nesting portion.The pawls 232 further include an arm 236 extending outwardly from thestem 234 and having a length sufficient to extend from the nestingportion through the remainder of the slots 228 and into the centralopening 226. The arm 236 is generally rectangular in shape and includesan outer end 238 that is positionable within the central opening 226. Toprevent the pawls 232 from interacting with the drive shaft 104 or thehousing 200, the length of each pawl 232 is sufficient that the majorityof the length of each pawl 232 is located within the housing collar 220.The overall length of the pawl 232 is such that when the pawls 232 areinserted fully into each slot 228 within the housing 220, a smallportion of each pawl 232 is positioned outwardly of the housing 220towards the cap 202, such that the pawls 232 can be engaged by the cap202 in a manner to be described.

The outer end 238 of the arm 236 of each pawl 232 is positionable withinthe central opening 226 in order to engage one of a number of teeth 240disposed on an outer surface 242 of a gear 244 rotatably disposed in theopening 226. The teeth 240 are formed of a size sufficient to enable thegear 244 to be rotated through an angle of about 210° in order to movethe width of a single tooth 240. Therefore, the size of the teeth 240allows for very small movements of the gear 244 with respect to thehousing collar 220 providing a “smooth” feel so that a fastener engagedby mechanism 218 can be very precisely adjusted. Also, because thesmaller size for the teeth 240 enables the teeth 240 to be positionedfurther from a central axis 245 of the gear 244, less stress or force isapplied directly to the interface of the pawls 232 and the teeth 240,lessening the chance of the pawls 232 slipping over the teeth 240.

The gear 244 is generally cylindrical in shape including a first section246 of the outer surface 242 on which the teeth 240 are disposed, and asecond section 248. As best shown in FIG. 8, the outer diameter of thefirst section 246 of the gear 244 defined by the teeth 240 is slightlyless than the inner diameter of the central opening 226, such that thegear 244 can rotate freely within the central opening 226 withoutinterference from the housing collar 220. However, the second section248 is held within the interior of the outer section 110 of the driveshaft 104 by bearing blocks 251 positioned around the second section 248and fixed to the drive shaft 104, such that the gear 244 can rotate withrespect to the drive shaft 104.

The gear 244 further defines a central aperture 250 extending into andthrough the first section 246, and including a number of spaced grooves(not shown) that extend the length of the aperture and which are adaptedto receive and engage complementary ridges (not shown) disposed on theshaft 108 in order to securely hold the shaft 108 within the gear 244and prevent slipping of the shaft 108 with respect to the gear 244.

The gear 244 is effectively prevented from rotating within the centralopening 226 of the housing collar 220 by the engagement of the pawls 232with the teeth 240 on the gear 244. The pawls 232 are biased intoengagement with the teeth 240 by a pair of biasing members 254 disposedon opposite sides of the central opening 226 adjacent each slot 228.

In a particularly preferred embodiment, each of the biasing members 254preferably includes a generally cylindrical pin 256 formed of a rigidmaterial that is inserted into an elongate pin hole (not shown) locatedin the housing collar 220 adjacent each slot 228. The length of each pin256 is preferably shorter than the length of each pawl 232, such thatwhen the pins 256 are inserted into the holes, the pins 256 do notextend outwardly from the housing collar 220. However, in an alternativeembodiment, the pins 256 can be formed to extend outwardly from theholes, for a purpose to be described

Each pin 256 is inserted through a central, looped portion (not shown)of a torsion spring 262 in order to anchor the spring 262 within thehousing collar 220. While the spring 262 is a preferred biasing elementfor use in the biasing members 254, other suitable elements can also beused, such as a resilient, deformable plastic member, or a leaf spring,among others. To anchor the spring 262, the central portion is insertedinto the pin hole for engagement by the pin 256 through a channel (notshown) that extends between and intersects both the pin hole and theslot 228. Thus, the spring 262 is positioned along the channel 264between the pin hole and slot 228. The engagement of the spring 262 withthe pawl 232 maintains the outer end 238 of the arm 236 in engagementwith the teeth 240 on the gear 244 to prevent rotation of the gear 244in a direction toward the respective pawl 232.

The pawls 232 are maintained in or disengaged from the teeth 240 on thegear 244 by recess 270 disposed on an interior surface 272 of the cap202. The portion of each pawl 232 extending outwardly from the slots 228is positioned within the recess 270 on the cap 202 when the cap 202 issecured to the housing collar 220. When the cap 202 is rotated over thehousing collar 220 such that the recess 270 comes into contact with theadjacent pawl 232, the pawl 232 is urged out of the central opening 226away from the teeth 240 against the bias of the biasing member 254 to adisengaged position. In this position, the gear 244 is allowed to rotatein a direction toward the disengaged pawl 232, as the opposite pawl 232is configured to allow rotation in this direction, but to prevent anyrotation of the gear 244 in the opposite direction. The cap 202 can beformed with a single recess 270 that can engage both pawls 232, or canhave two separate recesses 270, one to engage each pawl 232, such thatthe gear 244 can be made to rotate exclusively in either direction,depending on which pawl 232 is disengaged from the gear 244 by therecess(es) 270 on the cap 202.

In order to assist an individual in properly positioning the cap 202 toenable the recess 270 in the cap 202 to control the rotation of the gear244 in one direction or the other, the cap 202 includes a number ofdepressions (not shown) disposed adjacent the recess 270. Each of thedepressions is engageable with a spring-biased detent 282 positioned onthe housing collar 220. When the cap 202 is rotated, the detent 282 iscompressed inwardly into a bore (not shown) disposed in the housingcollar 220 that retains the detent 282 such that the cap 202 can rotateabove the detent 282. However when one of the depressions is positionedin alignment with the detent 282, a spring 283 positioned within thebore between the housing collar 220 and the detent 282 urges the detent282 outwardly into engagement with the depression. The cap 202 is thusheld in this position until such time as a sufficient force is appliedby an individual to the cap 202 to disengage the depression from thedetent 282. Further, to prevent the cap 202 from being rotated past theoutermost depressions, the recess 270 can be configured to engage eitherthe outwardly extending end of each pawl 232, or optionally with one ofthe pins 256 which functions as a stop for the rotation of the cap 202with respect to the housing collar 220.

The cap 202 can be rotatably secured to the exterior of the drive shaft104 in any conventional manner, but as shown in FIGS. 2 and 4, ispreferably secured to the drive shaft 104 by the engagement of acircumferential clip 284 disposed on the exterior of the drive shaft 104with a corresponding groove 286 disposed on the interior surface 272 ofthe cap 202. The engagement of the clip 284 and the groove 286 enablesthe cap 202 to rotate with respect to the drive shaft 104 and housingcollar 220 as necessary without disengaging the cap 202, unless desired.Further, by engaging the clip 284 within the groove 286, a centralopening 288 defined in the cap 202 is positioned in alignment with thecentral aperture 250 of the gear 244. Thus, the implement shaft 108 canbe inserted through the opening 203 in the cap 202 and into engagementwith the aperture 250 in the gear 244 in order to be utilized with theratcheting mechanism 218. Also, to assist in rotating the cap 202, thecap 202 can be formed of any suitable material, such as a metal or asuitably rigid plastic that can have added grip enhancements, such asknobs (not shown) or other high friction structures, or materials.

In addition, in the torque limiting mechanism 132′ for the tool 100shown in FIGS. 7-9, the plungers 134 have a different construction inwhich the projections 152 on which the springs 150 are seated areextended in length, and in which the concave surface 140 is removed, Inits place is disposed a single projection 290 that has a generallycircular cross-section. The projection is biased into engagement withthe grooves 128 on the engagement ring 120 in the manner describedpreviously, though the depth and shape of the grooves 128 are bothshallower and narrower than in the previous embodiment.

Referring now to FIG. 10, a third embodiment of the torque limitingmechanism 300 for use within the tool 100 is illustrated. In themechanism 300, the shaft 104 is integrally formed with a central section302 having a generally square-cross sectional area adjacent the innersection 112 of the drive shaft 104. A frictional cam member 304 isformed with a generally square-cross section aperture 306 extendingthrough the center thereof that is positionable around the centralsection 302 on the drive shaft 104 to secure the cam member 304 to thedrive shaft 104. The cam member 304 has an exterior surface 308 with anumber engaging surfaces 310 formed thereon that, in a preferredembodiment, is formed as a hexagonal surface 312. The hexagonal surface312 forms a number of flat friction panels 314 spaced equidistant aroundthe surface 312. The surfaces 314 on opposite sides of the cam member304 are engaged by plungers 316 having generally flat engaging surfaces318 that are pressed against the friction panels 314 as a result of thebias of compression members 148 that engage the plungers 316 in themanner described with regard to the previous embodiments for the torquelimiting mechanisms 132 and 132′. By adjusting the force exerted by thecompression members 148 on the plungers 316, the force required to shiftthe cam member 304 with regard to the plungers 316, thereby overcomingthe frictional forces created by the engagement of the panels 314 withthe surfaces 318, can be adjusted to provide the torque limitingmechanism 300 with an appropriate torque limiting value for the tool100.

Various other embodiments of the present invention are contemplated asbeing within the scope of the filed claims particularly pointing out anddistinctly claiming the subject matter regarded as the invention.

1. A torque limiting mechanism for a torque wrench comprising: a) acentral shaft including a first frictional engaging member disposedaround an exterior periphery of the shaft; b) at least one secondfrictional engaging member disposed in frictional engagement with thefirst frictional engaging member; and c) an adjustable biasing memberengaged with the second frictional engaging member and configured tobias the second frictional engaging member into engagement with thefirst frictional engagement member.
 2. The mechanism of claim 1 whereinthe first frictional engaging member includes a plurality of frictionpanels disposed around the periphery of the first frictional engagingmember that are engageable with the second frictional engaging member.3. The mechanism of claim 2 wherein the second frictional engagingmember includes an engagement surface selectively engageable with one ofthe plurality of engagement panels on the first frictional engagingmember.
 4. The mechanism of claim 1 wherein the first frictionalengaging member includes one of a number of depressions or a number ofpins positionable at least partially within the depressions, and whereinthe second frictional engaging member includes the other of the numberof depressions or the number of pins therein.
 5. The mechanism of claim1 comprising a pair of second frictional engaging members disposed onthe opposed sides of the central shaft.
 6. The mechanism of claim 5wherein the engaging members are disposed perpendicularly to the centralshaft.
 7. The mechanism of claim 1 further comprising an adjustmentmechanism engaged with the biasing member opposite the second frictionalengaging member.
 8. The mechanism of claim 1 wherein the firstfrictional engaging member is releasably connectable to the centralshaft.
 9. A torque wrench comprising: a) a handle having an openingtherein; b) a drive shaft disposed within the opening and extendingoutwardly from the handle, the drive shaft including a first frictionalengaging member disposed on the drive shaft; c) at least one secondfrictional engaging member engaged with the first frictional engagingmember; and d) a biasing member engaged with the at least one secondfrictional engaging member to urge the at least one second frictionalengaging member into engagement with the first frictional engagingmember; and e) an adjustment member engageable with the biasing memberopposite the at least one second frictional engaging member to controlthe force exerted by the biasing member on the at least one secondfrictional engaging member.
 10. The tool of claim 9 further comprising apair of second frictional engaging members disposed within the handleand engaged with opposite sides of the first frictional engaging member.11. The tool of claim 9 wherein the first frictional engaging memberincludes one of a number of bearings or a number of depressions in whichthe bearings rotatably seat spaced around the periphery of the firstfrictional engaging member.
 12. The tool of claim 11 wherein the atleast one second frictional engaging member further comprises the otherof a number of bearings or depressions in which the bearings rotatablyseat.
 13. The tool of claim 9 further comprising a ratcheting mechanismengaged with the drive shaft and spaced from the first frictionalengaging member.
 14. The tool of claim 13 wherein the ratchetingmechanism is at least partially disposed within the handle.
 15. The toolof claim 13 wherein the ratcheting mechanism is at least partiallydisposed within a collar formed on the drive shaft.
 16. The tool ofclaim 15 wherein the ratcheting mechanism further comprises: a) a gearrotatably disposed within the housing collar; and b) at least one pawlpivotably disposed in the housing collar and engageable with the gear.17. The tool of claim 16 wherein the ratcheting mechanism furthercomprises a cap secured to the housing collar over the gear, andselectively engageable with the at least one pawl.
 18. The tool of claim17 wherein the ratcheting mechanism includes a pair of pawls disposed onopposite sides of the housing collar, and wherein the cap is selectivelyengageable with each pawl to enable rotation of the gear in oppositedirections.
 19. The tool of claim 9 wherein the drive shaft is offsetwith regard to a center of the handle.